Many aesthetic dermatologic procedures resort to delivering thermal energy to skin or underlying subcutaneous tissue as a means to stimulate a therapeutic effect. Procedures such as skin resurfacing, skin tightening, wrinkle reduction, hair reduction, tattoo removal, body contouring, and treatments for excessive sweating, sebaceous gland production, acne, pigmented lesions, vascular lesions and blood vessels take advantage of heat to achieve a desired effect. Many different technologies can be used to heat the skin and/or underlying tissues including lasers, incoherent light sources, radiofrequency electrical energy sources, and ultrasound energy sources.
A problem with delivering RF energy to tissue is the fundamental concentration of current density along the edges of the electrode in contact with tissue. For monopolar RF energy delivery, higher skin surface temperatures occur along the entire perimeter of the electrode. For bipolar RF energy delivery, the concentration of current also occurs along the edges, but even higher current densities occur along the inner two edges forming the gap between the two electrodes having the shortest electrical path. These non-uniform thermal effects limit the amount of energy that can be delivered to tissue so as to avoid adverse skin effects such as burns, blisters, and erythema.